The plans have provoked fierce opposition in some quarters, including Anglican bishops who sit in the Lords.

The October debate in the Lords ended without a vote taking place.

But Lord Joffe, a former human rights lawyer, said he had modified his proposals in response to unease about incapacitated patients being actively helped to die by doctors.

The plans, similar to those already operating in the US state of Oregon, are now firmly centred on the principle that a person must self-administer a lethal dose.

Lord Joffe told the BBC: "I feel very strongly about assisted dying. It seems to me to be a human right to make a decision in relation not only to how you run your life, but how and when you die.

"Some terminally-ill patients suffer terrible deaths and the bill is all about preventing unnecessary suffering."

Safeguards

The cross bench peer said his proposed legislation was loaded with safeguards to prevent abuse.

It would require two doctors to state that the patient has less than six months to live, and two separate declarations by the patient, including one witnessed by a solicitor.

Lord Joffe said there was no evidence that assisted dying provisions had been abused in Oregon, or in other places where it is carried out, such as Switzerland and the Netherlands.

"Many of the opponents raise the question of a slippery slope," he said.

"But our bill is tightly drawn, there is no room for the courts or individuals to extend the law - that would need new legislation by future governments."

Critics

Leading critics of the proposals include Archbishop of Canterbury Dr Rowan Williams, who has written that life is "a gift from God that we cannot treat as a possession of our own to keep or throw away".

And in the Lords debate his predecessor as archbishop, Lord Carey of Clifton, said: "Medicalised killing is wrong.

"There are important civil reasons why society as a whole and its more vulnerable members would be threatened if the law were to be changed."

Matthew O'Gorman, from the charity Life, called on peers to reject the amended bill, which he said was an attempt to move towards fully legalised euthanasia.

He said: "Euthanasia is unnecessary and potentially dangerous - it takes away the safeguards that the vulnerable in our society deserve."

Health minister Lord Warner told peers in October that the government remained neutral on the issue, but said the bill raised "profound and complex ethical questions".

The British Medical Association dropped its long-held opposition to assisted dying in July, voting at its annual conference to adopt a neutral stance on the issue.